Articles | Volume 9, issue 2
Earth Syst. Dynam., 9, 507–523, 2018

Special issue: Social dynamics and planetary boundaries in Earth system...

Earth Syst. Dynam., 9, 507–523, 2018

Research article 17 May 2018

Research article | 17 May 2018

Analytically tractable climate–carbon cycle feedbacks under 21st century anthropogenic forcing

Steven J. Lade1,2,3, Jonathan F. Donges1,4, Ingo Fetzer1,3, John M. Anderies5, Christian Beer3,6, Sarah E. Cornell1, Thomas Gasser7, Jon Norberg1, Katherine Richardson8, Johan Rockström1, and Will Steffen1,2 Steven J. Lade et al.
  • 1Stockholm Resilience Centre, Stockholm University, Stockholm, Sweden
  • 2Fenner School of Environment and Society, The Australian National University, Australian Capital Territory, Canberra, Australia
  • 3Bolin Centre for Climate Research, Stockholm University, Stockholm, Sweden
  • 4Potsdam Institute for Climate Impact Research, Potsdam, Germany
  • 5School of Sustainability and School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, USA
  • 6Department of Environmental Science and Analytical Chemistry (ACES), Stockholm University, Stockholm, Sweden
  • 7International Institute for Applied Systems Analysis, Laxenburg, Austria
  • 8Center for Macroecology, Evolution, and Climate, University of Copenhagen, Natural History Museum of Denmark, Copenhagen, Denmark

Abstract. Changes to climate–carbon cycle feedbacks may significantly affect the Earth system's response to greenhouse gas emissions. These feedbacks are usually analysed from numerical output of complex and arguably opaque Earth system models. Here, we construct a stylised global climate–carbon cycle model, test its output against comprehensive Earth system models, and investigate the strengths of its climate–carbon cycle feedbacks analytically. The analytical expressions we obtain aid understanding of carbon cycle feedbacks and the operation of the carbon cycle. Specific results include that different feedback formalisms measure fundamentally the same climate–carbon cycle processes; temperature dependence of the solubility pump, biological pump, and CO2 solubility all contribute approximately equally to the ocean climate–carbon feedback; and concentration–carbon feedbacks may be more sensitive to future climate change than climate–carbon feedbacks. Simple models such as that developed here also provide workbenches for simple but mechanistically based explorations of Earth system processes, such as interactions and feedbacks between the planetary boundaries, that are currently too uncertain to be included in comprehensive Earth system models.

Short summary
Around half of the carbon that humans emit into the atmosphere each year is taken up on land (by trees) and in the ocean (by absorption). We construct a simple model of carbon uptake that, unlike the complex models that are usually used, can be analysed mathematically. Our results include that changes in atmospheric carbon may affect future carbon uptake more than changes in climate. Our simple model could also study mechanisms that are currently too uncertain for complex models.
Final-revised paper